This invention relates to an apparatus for spacing tubes of a heat exchanger tube bundle apart from one another and for reducing the vibration of the tubes during the operation of the heat exchanger.
Several different types of shell and tube heat exchangers are used for accomplishing indirect heat exchange between different mediums. Typical of such tube and shell heat exchangers are feedwater heaters, condensers and steam generators. In a tube and shell heat exchanger a tube bundle is disposed within a shell, and a heat exchange medium is passed through the tubes for indirect heat exchange with another heat exchange medium which is passed within the shell and over the outer surface of the tubes. In some heat exchangers the tube bundle comprises a group of straight tubes extending between an inlet header and an outlet header, with the tubes connected into tube sheets disposed at opposite ends of the shell. In other heat exchangers the bundle comprises a group of U-shaped tubes, with he tubes being secured at respective inlet and outlet ends to a single tubesheet, and the respective ends communicating with inlet and outlet headers. Regardless of the particular arrangement of the tube bundle, the tubes are axially spaced apart from one another, in order to expose the outer surface of each tube to the heat exchange medium which is passed over the tubes within the shell of the heat exchanger. The aforementioned tubesheets, as well as baffle plates and/or spacer assemblies, are used among other reasons to keep the tubes spaced apart from one another. The tubesheets, baffle plates and spacer assemblies are ordinarily installed during the fabrication of the heat exchanger.
If, after construction of the heat exchanger it is discovered that the tubesheets, baffles and spacer grids do not provide adequately for maintaining axial spacing of the tubes, it has heretofore been necessary to disassemble much of the heat exchanger, in order to relocate or install additional structural members, such as additional spacer grids, to correct such a problem. Furthermore, if after construction of the heat exchanger it is discovered that vibration of the tubes is occurring, it has heretofore been necessary to disassemble much of the heat exchanger, in order to install additional members, such as additional spacers which would serve to reduce or eliminate such vibration.
Known types of spacers, which have either been initially installed or retrofit, engage the tubes of the tube bundle substantially completely around the periphery of each tube with which it will come in contact and thereby will interfere with the flow of heat exchange medium along the outside surface of the tube in the direction along the length of each tube. Additionally, the known types of spacers, because they engage the tubes substantially completely around the periphery of the tubes, prevent the heat exchange medium flowing over the outside surface of the tubes from contacting that portion of the outer tube surface with which they come in contact.
The instant invention provides a helical spacer which can be installed either during the initial fabrication of a heat exchanger, or can be retrofit into an existing heat exchanger requiring substantially less disassembly of the heat exchanger. Additionally, the spacer of the instant invention allows for improved flow of heat exchange medium over the outer surface of the tubes of the tube bundle by reducing the area of contact between the tubes and the spacers, the effect of which is to reduce interference by the spacer with the flow of fluid in a direction along the length of the tube, and to make it possible for heat exchange medium to pass over more of the outer surface of the tubes than was possible with previously known spacers.